The newly developed exploration of shale oil and gas by hydraulic fracturing have decreased the demand for foreign oil and gas, while creating job opportunities and a plentiful clean energy source. However, sourcing water for hydraulic fracturing is challenging due to the high volume requirement in numerous remote locations. However, on a volume-volume ratio, the water-to-oil ratio (WOR) or water-to-oil-equivalent ratio for gas and oil from hydraulic fracturing is low as compared to conventional US oil production. On average, 3-5 million gallons of water are injected per well for hydraulic fracturing, and this water comes mainly from rivers and groundwater aquifers. For both cases, sudden withdrawals of large volumes of water could cause problems to environmental systems. Similarly, high volumes of produced water (generally called “flowback water”) comes back during oil and/or gas extraction.
The treatment of flowback water for reuse or disposal is difficult, because it often has high concentrations of total dissolved solids (TDS), environmentally regulated ions (e.g., Ba2+, Sr2+), and radioactivity (e.g., Ra2+). Direct discharge of the flowback water into surface water bodies would cause serious environmental damage, because of the waste water's high amounts of TDS and toxic/hazardous elements. Common treatment processes, such as reverse osmosis (RO) or landfilling, are not suitable for these wastes with high TDS values (3-6 times higher than sea water). Evaporation of the flowback water to solids, with consequent use in landfilling, is not feasible because the produced hazardous and radioactive solids would not pass EPA's Toxicity Characteristic Leaching Protocol (TCLP). Further, using hazardous waste landfills for all crystallized salts would be expensive, with prohibitive transportation costs. Deep well injections, on the other hand, require long distance transportation of very high volumes/weights of hazardous liquids.
There is a need in the art for a clean technology that allows for treating high-TDS waste water, such as Marcellus Shale gas flowback waste water. Such treatment processes technology should yield minimal amounts of water or salt waste without requiring externally added chemicals. The present invention addresses this need.